The present disclosure relates to curable silicone release coating compositions for laminate release applications.
Release coatings which are non-adherent to adhesives are known in the coatings art. For example paper release coatings are used to release adhesives, e.g pressure sensitive adhesives, from labels, decorative laminates, transfer tapes etc.
Polydimethylsiloxanes provide, when cross-linked, release coatings. This means that an adhesive-laminated face stock may be detached with very little force required which is desired for many release applications.
However, in various applications a higher release force is required for detachment. For example in laser printer application or at high speed converting machines, pre-dispensing has to be prevented by such a higher release level. Another example in which a higher release level is needed, is the usage in differential release liners wherein one side of the substrate is coated with a premium release silicone (low release forces) while the other side is coated with a tight (high release forces) release silicone layer.
Dependent on the application, a wide range of release force levels are required. The additives, which when mixed into a base polymer, modify the release characteristics in a controlled manner. These additives are referred to as controlled release additives (CRAs).
These control release additives can include a vinyl functional silicone resin, a siloxane fluid and optionally a reactive diluent such as an α-olefin or vinyl-ether to control composition viscosity below 10,000 centipoises. Examples of control release additives are disclosed in US 2011/0160376, US 2008/0311333, US 2007/0129507, US 2007/0087207, U.S. Pat. No. 7,846,550, U.S. Pat. No. 6,008,310, EP0601938B1, U.S. Pat. No. 6,124,419, U.S. Pat. No. 5,741,439, U.S. Pat. No. 5,708,075, U.S. Pat. No. 5,468,826, U.S. Pat. No. 5,468,816 and U.S. Pat. No. 4,611,042.
The release modifier compositions cited above can be produced through condensation of MQ resin with siloxane polymers. The release modifier compositions can have varying polymer or resin molecular weights and/or alkenyl content. The release compositions can incorporate “T” units into the MQ resin or the release compositions can included mixtures of lower/higher alkenyl or alkenyl/hydrogen MQ resins. The release compositions can cap hydroxyl MQ resins with various capping agents to impart different organo-functionalities such as alkenyl or hydrogen.
Still there remains a need for release modifier compositions that offer efficient release modification, reduced α-olefin or vinyl-ether content when used in the formulated release coating composition and no limitations as to type of adhesive used in the laminate.